Caesar

Caesar was a title in the Roman Empire that signified the heir apparent to the empire and/or the junior emperor. Emperor Claudius was the first to use the title "Caesar", during the Principate era, but it would first be applied in its later sense when Claudius made his stepson Nero his "caesar", his heir apparent. Under the Tetrarchy - formed by Diocletian in 293 - there were to be two men with the title Augustus, with each of them ruling a half of the empire; both of them would have junior emperors with the title caesar. This effectively created the Western Roman Empire and Eastern Roman Empire, and the title Caesar became the title for the junior emperors of both empires.